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Message-Id: <1649195156-9465-2-git-send-email-alan.maguire@oracle.com>
Date: Tue, 5 Apr 2022 22:45:55 +0100
From: Alan Maguire <alan.maguire@...cle.com>
To: andrii@...nel.org, daniel@...earbox.net, ast@...nel.org
Cc: kafai@...com, songliubraving@...com, yhs@...com,
john.fastabend@...il.com, kpsingh@...nel.org, bpf@...r.kernel.org,
netdev@...r.kernel.org, Alan Maguire <alan.maguire@...cle.com>
Subject: [PATCH bpf-next 1/2] libbpf: improve string handling for uprobe name-based attach
For uprobe attach, libraries are identified by matching a ".so"
substring in the binary path. This matches a lot of patterns that do
not conform to library .so[.version] suffixes, so instead match a ".so"
_suffix_, and if that fails match a ".so." substring for the versioned
library case.
For uprobe auto-attach, the parsing can be simplified for the SEC()
name to a single ssscanf(); the return value of the sscanf can then
be used to distinguish between sections that simply specify
"u[ret]probe" (and thus cannot auto-attach), those that specify
"u[ret]probe/binary_path:function+offset" etc.
Suggested-by: Andrii Nakryiko <andrii@...nel.org>
Signed-off-by: Alan Maguire <alan.maguire@...cle.com>
---
tools/lib/bpf/libbpf.c | 77 ++++++++++++++++-------------------------
tools/lib/bpf/libbpf_internal.h | 5 +++
2 files changed, 35 insertions(+), 47 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 91ce94b..3f23e88 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10750,7 +10750,7 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)
const char *search_paths[3] = {};
int i;
- if (strstr(file, ".so")) {
+ if (str_has_sfx(file, ".so") || strstr(file, ".so.")) {
search_paths[0] = getenv("LD_LIBRARY_PATH");
search_paths[1] = "/usr/lib64:/usr/lib";
search_paths[2] = arch_specific_lib_paths();
@@ -10897,60 +10897,43 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)
static int attach_uprobe(const struct bpf_program *prog, long cookie, struct bpf_link **link)
{
DECLARE_LIBBPF_OPTS(bpf_uprobe_opts, opts);
- char *func, *probe_name, *func_end;
- char *func_name, binary_path[512];
- unsigned long long raw_offset;
+ char *probe_type = NULL, *binary_path = NULL, *func_name = NULL;
+ int n, ret = -EINVAL;
size_t offset = 0;
- int n;
*link = NULL;
- opts.retprobe = str_has_pfx(prog->sec_name, "uretprobe");
- if (opts.retprobe)
- probe_name = prog->sec_name + sizeof("uretprobe") - 1;
- else
- probe_name = prog->sec_name + sizeof("uprobe") - 1;
- if (probe_name[0] == '/')
- probe_name++;
-
- /* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */
- if (strlen(probe_name) == 0)
- return 0;
-
- snprintf(binary_path, sizeof(binary_path), "%s", probe_name);
- /* ':' should be prior to function+offset */
- func_name = strrchr(binary_path, ':');
- if (!func_name) {
+ n = sscanf(prog->sec_name, "%m[^/]/%m[^:]:%m[a-zA-Z0-9_.]+%zu",
+ &probe_type, &binary_path, &func_name, &offset);
+ switch (n) {
+ case 1:
+ /* handle SEC("u[ret]probe") - format is valid, but auto-attach is impossible. */
+ ret = 0;
+ break;
+ case 2:
pr_warn("section '%s' missing ':function[+offset]' specification\n",
prog->sec_name);
- return -EINVAL;
- }
- func_name[0] = '\0';
- func_name++;
- n = sscanf(func_name, "%m[a-zA-Z0-9_.]+%li", &func, &offset);
- if (n < 1) {
- pr_warn("uprobe name '%s' is invalid\n", func_name);
- return -EINVAL;
- }
- if (opts.retprobe && offset != 0) {
- free(func);
- pr_warn("uretprobes do not support offset specification\n");
- return -EINVAL;
- }
-
- /* Is func a raw address? */
- errno = 0;
- raw_offset = strtoull(func, &func_end, 0);
- if (!errno && !*func_end) {
- free(func);
- func = NULL;
- offset = (size_t)raw_offset;
+ break;
+ case 3:
+ case 4:
+ opts.retprobe = str_has_pfx(prog->sec_name, "uretprobe");
+ if (opts.retprobe && offset != 0) {
+ pr_warn("uretprobes do not support offset specification\n");
+ break;
+ }
+ opts.func_name = func_name;
+ *link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);
+ ret = libbpf_get_error(*link);
+ break;
+ default:
+ pr_warn("uprobe name '%s' is invalid\n", prog->sec_name);
+ break;
}
- opts.func_name = func;
+ free(probe_type);
+ free(binary_path);
+ free(func_name);
- *link = bpf_program__attach_uprobe_opts(prog, -1, binary_path, offset, &opts);
- free(func);
- return libbpf_get_error(*link);
+ return ret;
}
struct bpf_link *bpf_program__attach_uprobe(const struct bpf_program *prog,
diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index b6247dc..155702a 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h
@@ -103,6 +103,11 @@
#define str_has_pfx(str, pfx) \
(strncmp(str, pfx, __builtin_constant_p(pfx) ? sizeof(pfx) - 1 : strlen(pfx)) == 0)
+/* similar for suffix */
+#define str_has_sfx(str, sfx) \
+ (strlen(sfx) <= strlen(str) ? \
+ strncmp(str + strlen(str) - strlen(sfx), sfx, strlen(sfx)) == 0 : 0)
+
/* Symbol versioning is different between static and shared library.
* Properly versioned symbols are needed for shared library, but
* only the symbol of the new version is needed for static library.
--
1.8.3.1
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